Indian tribe worries pipeline will disturb graves March 26, 2012 at 10:23 PM CDT - Updated June 26 at 8:26 PM By KATIE FRETLANDAssociated Press OKLAHOMA CITY (AP) - The chief of an Oklahoma tribe plans to voice his concerns about the Keystone XL pipeline this week in Washington. Sac and Fox Nation Chief George Thurman fears that workers would place the pipeline through sacred ground in Oklahoma without consideration of the tribe. The nation's historic preservation officer, Sandra Massey, says there are countless unmarked burial sites throughout the tribe's historic lands in north-central Oklahoma. President Barack Obama announced last week he was directing federal agencies to expedite the southern segment of the pipeline, which will run from Cushing, Okla., to Texas' Gulf Coast. A spokesman for Keystone pipeline operator TransCanada says the company works closely with tribes whenever its operations have a potential impact on their lands.